Cops are demonstrably not required to tell you they are cops. The idea that they need to was always ridiculous misinformation.
Meanwhile, as far as I'm aware, SWIM has not been the lynchpin in a court case yet, so it's hard to say one way or the other if using it as legal cover is actually a gross misconception.
It's a lot like the freemen-on-the-land folks. People think, against all evidence, that the law is a mindless machine, a slave to its inputs, unaffected by the human beings who actually administer it. They think you can hack the law by saying the right magic words, like Captain Kirk crashing an evil computer by saying "this sentence is false."
It doesn't work that way. If you try to buy 50 grams of coke off an undercover cop, no jury on earth is going to believe that you thought you were buying Coca-Cola. You're not going to get away with using a slang term universally understood to mean "me" and claiming it meant "someone else," either.
They are not.